The main goal of this proposal is to delineate the role and mechanisms of constitutive type II nuclear factor-kappa B (NF-kappa B) activation on adipogenesis. We, recently, have shown that the tumor necrosis factor (TNF) receptor-associated factor 3 (TRAF3) is a critical negative modulator of type II NF- kappa B pathway and TRAF3 knock out (TRAF3-/-) have constitutive activation of type II NF-kappa B. However, TRAF3-/- pups die within two weeks after birth and the function of TRAF3 remain largely elusive. TRAF3 null mice have greatly reduced serum glucose levels, elevated serum corticosterone and no brown fat. On the other hand, the development of pharmacological inhibitors of clAPs has been a major goal in advancing cancer therapeutics, as clAPs are believed to antagonize activated caspases and are often amplified in human cancers. Two reports using two different second generation SMAC mimetic compounds, including LBW242 showed that inhibition of clAPs can activate NF-KB noncanonically. As mentioned in proposed research plan, we have discovered that treatment with Smac/ LBW242 can prevent adipogenesis in 3T3-L1 preadipocyte cultures. We have found that both LBW242 and SM can inhibit PPAR gamma (master regulator of adipogenesis), C/EBPo and downstream adipocytes specific genes. Accomplishing our specific Aim 1-2, we will be able to understand whether metabolic abnormalities in TRAF3 null mice are due to defect in adipogenesis. From Aim 3, we will be able to understand the mechanism and important players involved in this inhibitory effect of adipogenesis. To accomplish all 4 Aims, we will use tissues, fibroblast cells and bone marrow cells from TRAF3-/-, NIK-/-, p100-/-, TRAF3-/- NIK-/-, TRAF3-/-p100-/-mice as well as 3T3-L1, ST2 and 3T3-F422A cell lines. Obesity is a major health concern in the United States. According to 2003-2004 National Health and Nutrition Examination Survey (NHANES), 66 percent of U.S. adults and 17 percent of children and adolescents are either overweight or obese. Aim 4 of our research plan is to delineate whether treatment with clAPs inhibitor LBW242 can reduce the weight and total adipogenesity in these mice. If we get significant data from these studies, we will be able to apply these findings to development of drugs to decrease fat accumulation and reduce adipogenesity. These drug can be indirectly apply to treating diabetes patients since obesity can lead to diabetes. By knowing exact mechanism(s) of inhibition of adipocyte differentiation caused by constitutive activation of type II NF-KB, we can also develop drugs other than LBW242 that can inhibit master regulators that promote adipogenesis with less side effects.